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<title>getservbyport_r()--Get Service Name for Port Number</title>
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<h2>getservbyport_r()--Get Service Name for Port Number</h2>
<div class="box" style="width: 60%;">
<br>
&nbsp;&nbsp;Syntax<br>
<pre>
#include &lt;netdb.h&gt;
int getservbyport_r(int <em>port_number</em>,
char *<em>protocol_name</em>,
struct servent *<em>servent_struct_addr</em>,
struct servent_data
*<em>servent_data_struct_addr</em>)
</pre>
<br>
&nbsp;&nbsp;Service Program Name: QSOSRV2<br>
<!-- iddvc RMBR -->
<br>
&nbsp;&nbsp;Default Public Authority: *USE<br>
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<br>
&nbsp;&nbsp;Threadsafe: Yes<br>
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<br>
</div>
<p>The <em>getservbyport_r()</em> function is used to retrieve information
about a service assigned to a port number. The information is retrieved from
the service database file.</p>
<br>
<h3>Parameters</h3>
<dl>
<dt>int <strong>port_number</strong> &nbsp;(input)&nbsp;</dt>
<dd>Specifies the port number for which service information is to be
retrieved.<br>
<br>
</dd>
<dt>char *<strong>protocol_name</strong> &nbsp;(input)&nbsp;</dt>
<dd>Specifies the pointer to the character string that contains the name of the
protocol that further qualifies the search criteria. For example, if the
<em>port_number</em> is 10, and the <em>protocol_name</em> is tcp, then the
call will return the server that uses the TCP protocol on port number 10. If
this parameter is set to NULL, then the first server is returned, regardless of
the protocol used.<br>
<br>
</dd>
<dt>struct servent *<strong>servent_struct_addr</strong>
&nbsp;(input/output)&nbsp;</dt>
<dd>Specifies the pointer to a servent structure where the results will be
placed. All results must be referenced through this structure.<br>
<br>
</dd>
<dt>struct servent_data *<strong>servent_data_struct_addr</strong>
&nbsp;(input/output)&nbsp;</dt>
<dd>Specifies the pointer to the servent_data structure, which is used to pass
and preserve results between function calls. The field serve_control_blk in the
servent_data structure must be initialized with hexadecimal zeros before its
initial use. If compatibility with other platforms is required then the entire
servent_data structure must be initialized with hexadecimal zeros before
initial use.</dd>
</dl>
<br>
<h3>Authorities</h3>
<p>No authorization is required.</p>
<br>
<h3>Return Value</h3>
<p>The <em>getservbyport_r()</em> function returns an integer. Possible values
are:</p>
<ul>
<li>-1 (unsuccessful call)</li>
<li>0 (successful call)</li>
</ul>
<p>The <strong>struct servent</strong> denoted by
<strong><em>servent_struct_addr</em></strong> and <strong>struct
servent_data</strong>denoted by
<strong><em>servent_data_struct_addr</em></strong> are both defined in
<strong>&lt;netdb.h&gt;</strong>. The structure <strong>struct
servent</strong>is defined as:</p>
<pre>
struct servent [
char *s_name;
char **s_aliases;
int s_port;
char *s_proto
];
</pre>
<p><em>s_name</em> points to the character string that contains the name of the
service. <em>s_aliases</em> is a pointer to a NULL-terminated list of pointers,
each of which points to a character string that represents an alternative name
for the service. <em>s_port</em> is the port number assigned to the service.
<em>s_proto</em> is a pointer to a character string that contains the name of
the protocol being used by the service.</p>
<br>
<h3>Error Conditions</h3>
<p>When the <em>getservbyport_r()</em> function fails, <em>errno</em> can be
set to:</p>
<dl>
<dt><em>[EINVAL]</em></dt>
<dd><p>The servent_data structure was not properly initialized with hexadecimal zeros before
initial use. For corrective action see the description for structure servent_data.</p></dd>
</dl>
<br>
<h3>Usage Notes</h3>
<ol>
<li>The iSeries Navigator or the following CL commands can be
used to access the services database file:<br>
<br>
<ul>
<li>WRKSRVTBLE (Work with Service Table Entries)</li>
<li>ADDSRVTBLE (Add Service Table Entry)</li>
<li>RMVSRVTBLE (Remove Service Table Entry)</li>
</ul>
<br>
</li>
<li>When the service information is obtained from the service database file,
the file is opened and the service information is retrieved (if it exists) from
the file. The file is then closed only if a <em>setservent_r()</em> call with a
non-zero parameter value was not previously done.<br>
<br>
</li>
<li>A coded character set identifier (CCSID) of 65535 for the job requests that
no database translation be performed. For translation to occur for the protocol
name specified by the <em>protocol_name</em> parameter, or for the service
names returned in the servent structure, the job CCSID must be something other
than 65535.</li>
</ol>
<br>
<h3>Related Information</h3>
<ul>
<li><a href="tsgservn.htm">getservbyname_r()</a>--Get Port Number for Service
Name<br>
<br>
</li>
<li><a href="tsgserve.htm">getservent_r()</a>--Get Next Entry from Service
Database<br>
<br>
</li>
<li><a href="tssserve.htm">setservent_r(</a>)--Open Service Database<br>
<br>
</li>
<li><a href="tseserve.htm">endservent_r()</a>--Close Service Database</li>
</ul>
<br>
<hr>
API introduced: V3R1
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